Such methods for producing plant protection or plant- strengthening agent for controlling bacterial and/or fungal plant diseases, in particular for controlling fire blight, are known in a variety of forms and embodiments.
It is known that antagonistic microorganisms are employed more and more often. Besides bacteria such as, for example, Bacillus thuringiensis, which are used as insecticides, or Bacillus subtilis, which are used in soil treatment agents and seed-dressing products, there are also preparations comprising fungal spores and yeast cells.
A known example is the plant protection production Contans, which comprises spores of Coniothyrium minitans, or various preparations with the yeast Trichoderma harzianum. These preparations are essentially applied to the soil or incorporated into the soil or garden compost. These agents are not suitable for floral application.
The disadvantage is that fire blight of pome fruit is caused by the bacterium Erwina amylovora. It is controlled for example by plant management methods and sanitation, for example by grubbing up the plants, for example reduction of the inoculum. Fire blight is furthermore controlled by means of plant protection agents. Frequently, treatments with antibiotics are carried out during flowering. Here, the active substance streptomycin, whose activity is well known, is used. However, this plant protection agent has recently been banned, or will be banned all over the EU. The active substance streptomycin, which the plant protection agent plantomycin contains, has been used successfully in the United States since the 70s; however, problems with resistant pathogens are on the increase, which is undesired.
Also known are treatments with copper during flowering, for example with funguran, cuprozin; however, they must not be carried out in the case of dessert fruit as the result of phytotoxic effects. Moreover, the license of this agent has already expired in December 2002.
Moreover, there have been attempts to apply antagonistic microorganisms to the flowers of fruit trees and thus to inhibit the growth of pathogen and thus to prevent infection. Various bacteria such as Pseudomonas flourescens, Pantoea agglomerans, Bacillus subtilis, Rhanella aquatilis, have been employed in this context. In some cases, saleable products were developed with these bacteria, such as, for example, the products Blight ban and Serenade in the USA and BIOPRO in Germany. The effects of these products are very dubious to date, and their use is very limited.
It is therefore an object of the present invention to provide a method for producing plant protection agent for controlling bacterial and/or fungal plant diseases, in particular fire blight, and a plant protection agent and its use which overcome the above-mentioned disadvantages and which can be employed highly effectively for a multiplicity of plants, in particular fruit plants. In this context, it is intended that the plant protection agent can be applied to the diseased plants in sprayable form.